DNS- name change doesn't delete old computers

[Manico12303]

Hello... i installed track-it 8 and was using it's inventory features, when i noticed an odd problem, devices that did not exsist or have had a name change still had the old devices appear. after much research, and calling tech support, I realised the issue was related to the fact that when my company changed the naming convention on client machines and started to implement it, the "old names" did not disappear from DNS. Am i wrong to assume active directory and DNS should handle this automatically. Was wondering if someone might shed some light on the "best practice" for implementing this change, and what might be wrong with DNS. It's just odd being able to resolve a name that has been changed on our system sometimes up to a year ago.

Thank you in advance, and please keep it as strait to the point as possible, i am our companies junior admin /tech for the last year and a half, but am still learning.

Manico
Upstate Ny